/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements.  See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership.  The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License.  You may obtain a copy of the License at
*
*   http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied.  See the License for the
* specific language governing permissions and limitations
* under the License.    
*/

namespace NVelocity.Runtime.Parser
{
	using System;
    /// <summary> This interface describes a character stream that maintains line and
    /// column number positions of the characters.  It also has the capability
    /// to backup the stream to some extent.  An implementation of this
    /// interface is used in the TokenManager implementation generated by
    /// JavaCCParser.
    /// 
    /// All the methods except backup can be implemented in any fashion. backup
    /// needs to be implemented correctly for the correct operation of the lexer.
    /// Rest of the methods are all used to Get information like line number,
    /// column number and the String that constitutes a token and are not used
    /// by the lexer. Hence their implementation won't affect the generated lexer's
    /// operation.
    /// </summary>

    public interface ICharStream
    {
        /// <summary> Returns the column number of the last character for current token (being
        /// matched after the last call to BeginTOken).
        /// </summary>
        int EndColumn
        {
            get;

        }
        /// <summary> Returns the line number of the last character for current token (being
        /// matched after the last call to BeginTOken).
        /// </summary>
        int EndLine
        {
            get;

        }
        /// <summary> Returns the column number of the first character for current token (being
        /// matched after the last call to BeginTOken).
        /// </summary>
        int BeginColumn
        {
            get;

        }
        /// <summary> Returns the line number of the first character for current token (being
        /// matched after the last call to BeginTOken).
        /// </summary>
        int BeginLine
        {
            get;

        }

        /// <summary> Returns the next character from the selected input.  The method
        /// of selecting the input is the responsibility of the class
        /// implementing this interface.  Can throw any java.io.IOException.
        /// </summary>
        char ReadChar();

        /// <summary> Backs up the input stream by amount steps. Lexer calls this method if it
        /// had already read some characters, but could not use them to match a
        /// (longer) token. So, they will be used again as the prefix of the next
        /// token and it is the implemetation's responsibility to do this right.
        /// </summary>
        void Backup(int amount);

        /// <summary> Returns the next character that marks the beginning of the next token.
        /// All characters must remain in the buffer between two successive calls
        /// to this method to implement backup correctly.
        /// </summary>
        char BeginToken();

        /// <summary> Returns a string made up of characters from the marked token beginning 
        /// to the current buffer position. Implementations have the choice of returning
        /// anything that they want to. For example, for efficiency, one might decide
        /// to just return null, which is a valid implementation.
        /// </summary>
        string GetImage();

        /// <summary> Returns an array of characters that make up the suffix of length 'len' for
        /// the currently matched token. This is used to build up the matched string
        /// for use in actions in the case of MORE. A simple and inefficient
        /// implementation of this is as follows :
        /// 
        /// {
        /// String t = GetImage();
        /// return t.substring(t.length() - len, t.length()).toCharArray();
        /// }
        /// </summary>
        char[] GetSuffix(int len);

        /// <summary> The lexer calls this function to indicate that it is done with the stream
        /// and hence implementations can free any resources held by this class.
        /// Again, the body of this function can be just empty and it will not
        /// affect the lexer's operation.
        /// </summary>
        void Done();
    }
}